docs: Remove ubuntu installation guide

The installation guide points to 1.x packages from OBS.  For 2.x we
decided to stop building packages on OBS in favour of advertising
kata-deploy.

Apart from this, Ubuntu itself doesn't provide packages for
kata-containers.

Fixes: #1588

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>

docs/install/ubuntu-installation-guide.md

@@ -1,15 +0,0 @@
-# Install Kata Containers on Ubuntu
-
-1. Install the Kata Containers components with the following commands:
-
-   ```bash
-   $ ARCH=$(arch)
-   $ BRANCH="${BRANCH:-master}"
-   $ sudo sh -c "echo 'deb http://download.opensuse.org/repositories/home:/katacontainers:/releases:/${ARCH}:/${BRANCH}/xUbuntu_$(lsb_release -rs)/ /' > /etc/apt/sources.list.d/kata-containers.list"
-   $ curl -sL  http://download.opensuse.org/repositories/home:/katacontainers:/releases:/${ARCH}:/${BRANCH}/xUbuntu_$(lsb_release -rs)/Release.key | sudo apt-key add -
-   $ sudo -E apt-get update
-   $ sudo -E apt-get -y install kata-runtime kata-proxy kata-shim
-   ```
-
-2. Decide which container manager to use and select the corresponding link that follows:
-   - [Kubernetes](../Developer-Guide.md#run-kata-containers-with-kubernetes)

docs/use-cases/zun_kata.md

@@ -10,9 +10,6 @@ Currently, the instructions are based on the following links:
 
 - https://docs.openstack.org/zun/latest/admin/clear-containers.html
 
-- ../install/ubuntu-installation-guide.md
-
-
 ## Install Git to use with DevStack
 
 ```sh
@@ -54,7 +51,7 @@ $ zun delete test
 
 ## Install Kata Containers
 
-Follow [these instructions](../install/ubuntu-installation-guide.md)
+Follow [these instructions](../install/README.md)
 to install the Kata Containers components.
 
 ## Update Docker with new Kata Containers runtime